Head of the Laboratory of Metallurgy in Mechanical Engineering, D.Sc. in Eng., Associate ProfessorSANDOMIRSKYSergey Grigoryevich

Areas of activities

DEVELOPMENT OF CHEMICAL-THERMAL HARDENING TECHNOLOGIES APPLIED TO SPECIAL EQUIPMENT THAT PROVIDE THE REQUIRED QUALITY OF POWER TRANSMISSION PARTS FOR AUTOMOTIVE EQUIPMENT

On the basis of the software at the design stage, the steel brand, technical requirements for the effective thickness and quality of the hardened layers microstructure are assigned, the technological modes of chemical and thermal processing are developed.Methods of material quality control (patents no. 14748, 15273) allow to identify microstructural state defects, which are not detected by conventional methods in mechanical engineering, but have a significant impact on the performance of products.The technology corresponds to the best world analogues (Caterpillar, Mercedes-Benz, Volvo, Komatsu, Unit Rig, General Electric, etc.).Works on the development of advanced technologies of thermochemical treatment are made at OJSC “Minsk Wheel Tractor Plant”, OJSC “BELAZ”, Minsk Tractor Works.The research results allow to reduce energy and material costs to 30 % by using sparingly alloyed steels, to improve the service life of parts by 1.2–1.5 times due to the increase in the endurance limits of the material and the quality of hardening.

The software package for the design of technological processes of thermochemical treatment transmissions gears includes:

a software package for calculation and prediction at the design stage of the reliability index of transmissions gears (fig. 1) taking into account the operating conditions and design of the transmission, the geometric parameters of the gear clutch, steel brand, manufacturing technology and quality of chemical and heat treatment, as well as a database on the effect of the structure quality of the hardened layers and features of the applied thermal equipment on the characteristics of bending and contact fatigue of the gears. The output data at this stage are the design parameters of the gear drive and the technical requirements for the steel brand, the distribution of microhardness over the thickness of the hardened layer (effective thickness) and the quality of the microstructure, providing a defined durability;

the software package for the calculation of the chemical-thermal treatment modes, consisting of a program for calculating steel hardenability (fig. 2) and a program for calculating the process of carbon diffusion into steel, depending on the steel brand, carburizing and heat hardening parameters (fig. 3). The calculation output data are the concentration of the carbon potential and the temperature-time intervals of each stage of the technical process of thermochemical treatment.

The application of software package for control of thermochemical treatment processing allows ensuring the required level of reliability at design stage not only to choose the design parameters of gears, but also, depending on the level of load and the required durability, to assign a steel brand, technical requirements for the effective thickness and quality of hardened layers microstructure, to develop technological modes of chemical and thermal treatment for each specific type of transmission. Moreover, when changing the conditions of heat treatment and the components variety, it is possible to quickly reconfigure the technological process, which increases the productivity of the production processes of thermochemical treatment.

MAGNETIC STRUCTUROSCOPY OF IRON-CARBON ALLOYS

Studies focus on the analysis of the features of the relations of structural and phase composition, physical and mechanical properties of steel and cast iron with their magnetic parameters. The established features and patterns helped to develop new high-performance methods of non-destructive quality control of the structure of steel and cast iron products, including moving ones in the production process.

Results:

The physical principles of using the notion of "demagnetization coefficient" in the calculations of the process and the result of magnetization of a ferromagnetic body are generalized. A logical chain is built from the classic calculations of the demagnetization coefficient of the ellipsoid to the interpolation formulas for the calculation of demagnetization factors of inhomogeneously magnetized bodies. The features of cast iron magnetization under the influence of internal demagnetization of graphite inclusions are established.

The features of the connection between the structure and physical and mechanical properties of iron with their magnetic parameters are established. For example, a quantitative relation between the content of ferrite and the residual magnetic flux Фd (in µWb) in ductile iron flashings KCh30-6 is defined. The appearance of ledeburite and secondary cementite (chill) in the structure of the flashing increases the gauge readings.

The results of studies and technical solutions for the provision of defined structure of not tooled casting nipples from ductile iron were given to the Minsk plant of heating equipment according to license agreements and were implemented in the Production unit of ductile and grey cast iron as part of the automated line of monitoring and automatic sorting according to the machinability of the casting nipples from ductile iron KCh30-6.

The operation of the line increased the profitability of the production of nipples, provided the need for the plant, allowed to not replace iron nipples with imported steel ones, to provide their export supplies.

Analytical expressions for the calculation of relaxation magnetic parameters of steels by the parameters of the major hysteresis loop are gained, as well as for the evaluation of the maximum magnetic permeability of steels and cast irons by the coercive force, the calculation of the maximum magnetic permeability of steels and the error of its measurement, the formula for calculating the residual magnetization of steels as the average value of the reliable variation range.

The established regularities allow to develop reliable and productive methods of quality control of structure of steel and cast iron products, including moving ones in the production process. More than 20 patents of the Republic of Belarus are obtained for the developed technical solutions.The work resulted in an improved method of controlling the mechanical properties of heat-treated bolts of diesel engines. Method of electromagnetic control of mechanical properties of moving ferromagnetic products was given to the branch of the Minsk motor plant in the town Stolbtsy according to the license agreement and was put into production. The use of the method implemented by the developed MAKSI-U device (magnetic analyzer of products construction quality) guarantees a defined stress limit of bolts, increases the reliability of all diesel engines produced by the Minsk motor plant.Method application also brings direct economic effect to the plant – thousands of expensive bolts were returned to production.

The developed method of magnetic control of the thickness of the surface-hardened layers of extended products was given to JSC "Minsk motor plant" and implemented in the Automatic production unit of JSC "Minsk motor plant" of a branch in town Stolbtsy. The increase in the control reliability is achieved due to the fact that the information parameter of the method at high sensitivity to the thickness of the surface-hardened layer is practically not affected by the non-stability of the position of the products during magnetization and measurement. A developed automated local surface hardening quality classifier of small steel products is in operation in the production unit.

The methods application prevented the emergence of essential axles with a low level of mechanical properties at assembly conveyer of the Minsk motor plant and increased the reliability of all diesel engines produced by the plant.

Implementation of the results and studies allows to guarantee a defined level of physical and mechanical properties of essential products of mechanical engineering and metallurgy.

RESEARCH AND DEVELOPMENT OF TECHNOLOGICAL FUNDAMENTALS OF RING-ROLLING OF PARTS SUCH AS RINGS

At the enterprises of Belarus (Minsk Bearing Plant, Minsk Tractor Works, Minsk Automobile Plant, BelAZ, Minsk Wheel Tractor Plant, etc.), the total number of manufactured parts that have the shape of rings is more than 100 items when the production program is about 160,000 pcs. The metal utilization factor is about 0.6. About 4,000 tons of shavings are formed. Domestic plants have no experience in the use of ring rolling complexes, but purchase of such complexes is considered by the Minsk Bearing Plant and BelAZ.

It is assumed that the new technology will increase the metal utilization rate to 0.8. The research carried out at the Institute is aimed at scientific support for the introduction of new equipment.

Sandomirsky, S.G. Analysis of the Distribution of Magnetization Along a Rod Made of a Material with a High Magnetic Susceptibility / S.G. Sandomirsky // Measurement Techniques. June 2016, Volume 59, Issue 3, pp 272–276.